The eye fundus is a medical term used to describe the structures at the posterior of a human eye (i.e., the interior lining of the eye), including the retina, optic disc (i.e., blind spot) and macula (i.e., fovea). Fundus observation devices, opthalmoscopes, and retinal cameras, are known in the art. Generally, a retinal observation device is placed at a predetermined distance in front of the examined eye. The observation device provides illumination to the retina through the eye pupil and forms a retinal image outside of the eye, by light reflected from the retina. An image detector detects this image, and a physician or an eye examiner may view this image using a display or an eyepiece.
Stereoscopic retinal cameras and opthalmoscopes are known in the art. Such cameras generally operate similarly to monocular retinal cameras, with the addition of a light guidance element (e.g., two-hole diaphragm) in order to split the light beam coming from the retina into two separate light beams (i.e., a right view and a left view). The split light beams traverse a path through two optical systems (i.e., a right view system and a left view system) toward two separate image detectors, which detect a right image and a left image of the retina. Alternatively, the right view and left view light beams traverse a path through the two optical systems toward a pair of eye-pieces, which are used by the physician for stereoscopic observation of the retina (e.g., each of the right and left view images are respectively provided to the right and left eyes of the physician).
Retinal cameras and opthalmoscopes can be utilized for biometric retinal imaging. Since the patterns of blood vessels on the retina are unique to each individual, this information can be used for the identification or identity verification of an individual (e.g., for allowing or denying access to certain areas or rooms in military compounds, power plants or other locations which are considered of high security classification, for allowing or denying performance of certain actions, such as cash retrieval from an ATM and the like). Retinal scanning devices are known in the art. Such devices scan the retina, analyze the patterns in the layer of blood vessels at the back of the eye and compare these patterns to files stored in a database, in order to identify or verify the identity of an individual.
U.S. Pat. No. 5,506,634 issued to Wei et al. and entitled “Fundus Illumination Apparatus Formed From Three, Separated Radiation Path System” is directed to an apparatus for illuminating a fundus of an eye using a beam of light. The apparatus includes an optical illumination path system and an optical observation path system. The optical illumination path system includes an incandescent light source, a first lens, a stop aperture, a first glass prism, a second lens, a third lens, a near-infrared filter and a second glass prism. The optical observation path system includes an ocular lens, a beam splitter, a first lens, a stop aperture, a second lens and a CCD camera. The observation path system is located directly in front of a photographed eye, and the illumination path system is located at a tilt angle with respect to the optical axis of the observation path system.
The light source emits light a beam, which passes through the first lens, the stop aperture, the first glass prism, the second lens, the third lens, the near-infrared filter and through the second glass prism. The light beam then impinges on the beam splitter, which directs it toward the ocular lens and into the eye. The light beam is reflected off of the fundus of the eye and passes through the ocular lens, the beam splitter, the first lens, the stop aperture and through the second lens, toward the CCD camera. The CCD camera is located on the focal plane of the combined assembly of the first lens, the stop aperture and the second lens, where an image of the fundus is obtained.
U.S. Pat. No. 5,355,253 issued to Nanjo et al. and entitled “Stereoscopic Retinal Camera” is directed to a system for photographing and observing an eye fundus in a stereoscopic manner. The system includes an illuminating optical section and a photographing optical section. The illuminating optical section includes a halogen lamp, a plurality of condenser lenses, a flash lamp, a beam splitter, a relay lens, a mirror, an aperture diaphragm and a perforated mirror.
The illuminating optical section is placed in a perpendicular manner to the optical axis of the photographing optical section, such that light beams emitted from the halogen lamp and the flash lamp are deflected toward of the eye. The aperture diaphragm has a circular slit, passing there through light beams emitted from the halogen lamp. The light beams are deflected by the mirror toward the optical axis of the photographing optical section. The condenser lens creates an image of the aperture diaphragm slit near the opening of the perforated mirror. The intermediate image of the slit is reflected by the perforated mirror, and the objective lens focuses the image of the slit near the eye cornea to illuminate the eye fundus.
The photographing optical section includes an objective lens, a two-hole diaphragm, a light splitting prism, two beam splitting prisms, two relay lenses, two focusing lenses, two image forming lenses and two films. The light splitting prism is a triangular shaped prism, located on the optical axis of the photographing optical section, such that the base of the triangle is perpendicular to the optical axis, facing the objective lens. The two-hole diaphragm is adjacent to the base of the triangular light splitting prism. The photographing optical section is placed in front of the eye, such that light beams reflected from the fundus are directed at the objective lens and the light splitting prism.
A light beam reflected from the fundus is focused by the objective lens, passes through the opening of the perforated mirror, through the two-hole diaphragm and into the light splitting prism. Light passing through the two-hole diaphragm is split into a right light beam and a left light beam. The light splitting prism interchanges the right light beam and the left light beam with each other, since the light beams originate in an inverted image of the fundus. The two beam splitting prisms collimate the right and left light beams, so that the collimated light beams pass along two parallel paths separated by a predetermined distance.
The separated light beams pass through the two relay lenses respectively, through the two focusing lenses and through the two image forming lenses. The image forming lenses form a right image and a left image of the fundus on the two films, respectively. The two focusing lenses are movable along the optical axis of the photographing optical system. The positions of the focusing lenses are adjusted according to the refracting power of the eye, to focus the image of the fundus on the each film. The two films then present images of the fundus, as viewed from two different viewpoints.
U.S. Pat. No. 6,726,326 B2 issued to Fukuma et al. and entitled “Observation Apparatus” is directed to an apparatus for observing an eye fundus, with an astigmatism canceling optical element. The apparatus includes an illumination optical system and an observation optical system. The illumination optical system includes a light source, a condenser lens, an illumination field stop, a collimator lens and a prism. The light source emits light toward the objective lens, which is also used by the observation optical system. The light passes through the condenser lens, the illumination field stop, the collimator lens and through the prism toward an eye fundus of an operating eye, so that the eye fundus is illuminated.
The observation optical system includes a right-eye observation optical system and a left-eye observation optical system. Each of the right-eye and the left-eye observation optical systems includes a zoom lens system, a beam splitter, an imaging lens, an image erecting prism, an interpupillary distance adjustment prism, a field stop, an eyepiece and an astigmatism canceling optical element. Each zoom lens system is composed of three lenses. Light reflected from the eye fundus is directed to the eyes of an apparatus operator through the objective lens and through the optical members of the right-eye and left-eye observation optical systems, so that the operator observes the eye fundus with both the right and left eyes.
A portion of the reflected light from the eye fundus is directed by a beam splitter toward an auxiliary observation optical system, for an assistant operator or toward an image pickup device, for producing an image of the eye fundus.
The astigmatism canceling optical element is utilized for canceling astigmatism power, caused when the optical members (i.e., lenses, mirrors and the like) are held against the cornea of the examined eye. The astigmatism canceling optical element includes a first and a second variable cylindrical lenses. The astigmatism canceling optical element is located between the zoom lens system and the imaging lens, in each of the right-eye and left-eye observation optical systems. The first variable cylindrical lens is composed of a convex cylindrical lens and the second variable cylindrical lens is composed of a concave cylindrical lens. The variable cylindrical lenses are located so as to be integrally rotatable about the observation optical axes, and to be rotatable relative to each other. When the variable cylindrical lenses are integrally rotated about the observation optical axes, the orientation of the astigmatism canceling optical element can be made to correspond to the orientation of the astigmatism caused according to how the optical members of the apparatus are held against the eye. In this manner, astigmatism canceling optical element is used to cancel the astigmatism of the examined eye.